This invention relates to a liquid filter, especially an oil filter, for cleaning lubricating oil, especially for internal combustion engines in motor vehicles, having the features of the definition of the species of claim 1.
German Patent 39 03 675 C2 describes an oil filter of this type, having a filter housing arranged essentially upright in the installed state and containing a receiving area for a ring-shaped filter insert inserted into it for filtering the oil. The filter housing is also equipped with an inlet for the unclean oil which flows around the ring-shaped filter insert. In addition, an outlet for the cleaned oil is also provided and is connected to a central inside area of the filter housing and is accommodated in a bottom on the lower end of the receiving area. The known oil filter is also equipped with an additional discharge channel out of the receiving area, provided on the bottom of the receiving area. A pin extending parallel to the longitudinal axis of the ring-shaped filter insert and projecting eccentrically thereto is molded onto a lower end disk of the ring-shaped filter insert; when the ring-shaped filter insert is inserted into the filter housing, the pin penetrates through an opening in the discharge channel and seals it. Such a discharge channel is needed to empty the receiving area for changing the ring-shaped filter insert, thus reducing the risk of soiling. With the known oil filter, when the ring-shaped filter insert is removed, the discharge channel is automatically released, so that the oil in the receiving area can flow out, preferably into an oil pan.
The known oil filter has positioning means which guarantee that the ring-shaped filter insert is always positioned relative to the filter housing on insertion of the ring-shaped filter insert so that the pin penetrates axially into the opening in the discharge channel. A web which projects radially inward and extends axially is formed on the inside wall of the filter housing, where it serves as a positioning means, engaging in a radial slot formed on the outside circumference of the lower end disk of the ring-shaped filter insert. The problem here is that threading the web into the radial slot requires careful handling.
The present invention is concerned with the problem of designing a filter of the type defined above so that insertion of the ring-shaped filter insert is simplified.
This problem is solved according to this invention by a liquid filter, especially an oil filter, for cleaning lubricating oil, especially having the features of claim 1.
This invention is based on the general idea of arranging an insertion aid on the bottom of the receiving area to ensure that the pin will always find the opening in the discharge channel on insertion of the ring-shaped filter insert, regardless of the relative initial position of the ring-shaped filter insert with respect to the filter housing. As an insertion aid, a ramp is proposed, so that the pin always encounters the ramp on axial insertion of the ring-shaped filter insert if the pin is not aligned with the opening in the discharge channel. The ramp drops in the direction of the opening in the discharge channel so that the pin slides along the ramp to reach the opening at the lower end of the ramp. The ring-shaped filter insert is designed specifically so that the pin is able to slide along the ramp. First, special contact zones which permit sliding may be formed on the pin as well as the ramp. Second, the ring-shaped filter insert is designed so that it can rotate freely about its longitudinal axis in the receiving area of the filter housing.
According to a special embodiment, the ramp may be designed to be helical and it may have an essentially complete winding, so that then an upper end of the ramp is adjacent to the opening in the discharge channel. Accordingly, the lower end of the ramp is located on one side at the opening in the discharge channel and on the other side is the upper end of the ramp, with an inclined flank optionally being formed between the opening and the upper end of the ramp. If the filter housing has a cover which can be screwed onto the filter housing to close it, the ramp drops toward the opening in the discharge channel in the direction of screwing on the cover. This measure guarantees that screwing on the cover will support the pin sliding along the ramp.
According to another especially advantageous embodiment, a guide contour may be formed at least in a section of the ramp containing the lower end of the ramp next to the contact zone of the ramp radially, said contour projecting axially beyond the contact zone of the ramp toward the receiving area. This measure makes it possible to implement a radial guide for the pin sliding along the ramp, thus making it simpler for the pin to find the opening in the discharge channel. The risk of the ring-shaped filter insert becoming skewed radially in the filter housing on insertion of the ring-shaped filter insert is thus reduced. Radial manufacturing tolerances can also be equalized due to the proposed guide contours.
Two radially opposed guide contours are preferably provided, with the contact zone of the ramp running between them. In addition, these guide contours may also have an insertion flank on an end facing away from the opening in the discharge channel. The proposed measures produce an improved radial guidance of the pin.
According to an advantageous embodiment, a projection extending axially away from the pin may be designed on an end of the pin facing the ramp, the free end axially forming the contact zone of the pin. As a result of this measure, the contact zones that work together can be optimized in an especially simple manner, thus achieving an especially low adhesive and sliding friction between the pin and the ramp. This improves sliding of the pin along the ramp and thus reliable threading of the pin into the opening in the discharge channel.
The projection is preferably thinner in at least one axially free end area in the radial direction than the radial distance between two radially opposed guide contours, and in particular the projection is longer in the axial direction in the axial distance between the contact zone of the ramp and an upper end of the guide contours. In this embodiment, the radial guidance by the guide contours can be implemented by a cooperation with the axial projection on the pin, so that only a reduced amount of space is needed for the ramp.
In another embodiment of this invention, the pin may be mounted flexibly on the end disk. Through this measure, radial manufacturing tolerances in the manufacture of the filter housing can be equalized. There is automatically an equalization of tolerance in the circumferential direction due to the free rotatability of the ring-shaped filter insert.
To improve sliding of the pin along the ramp, a tapering end section having the contact zone of the pin may be formed on the axially free end of the pin. In this way, a small area (in comparison with the cross section of the pin at the beginning of the end section) can be created especially easily as the contact zone of the pin on in particular a spot-shaped or linear contact zone may be created.
In a refinement of this invention, in order for the pin to be able to overcome obstacles such as soiling, deposits, etc, as it slides along the ramp, it is adjustably mounted on the end disk and/or the ring-shaped filter insert is adjustably mounted on the cover, and in particular it is under a spring bias toward the ramp.
In a preferred embodiment of this invention, the filter housing may be closed with a screw-on cover, and restraining devices are provided for mounting the ring-shaped filter insert on the cover in such a way that it is rotatable about its longitudinal axis and is secured axially. These restraining devices have catch hooks which extend essentially axially and are flexible radially. In addition, the restraining device also include a radially projecting ring-shaped shoulder on which the catch hooks are engaged when the ring-shaped filter insert is placed onto the cover. The upper end disk has a central orifice on the edge of which are arranged a gasket and an axially protruding ring-shaped collar. In addition, an axially protruding central ring is also mounted on the cover, said ring being arranged coaxially with the ring-shaped collar when the ring-shaped filter insert is placed on the cover, with the gasket forming a seal radially between the ring an the ring-shaped collar. This forms an especially inexpensive plug-in connection between the ring-shaped filter insert and the housing cover, forming an effective seal between the inside and the outside of the ring-shaped filter insert at the same time.
Other important features and advantages of the device according to this invention are derived from the subclaims, the drawings and the respective description of the figures on the basis of the drawings.
It is self-evident that the features mentioned above and those to be explained below can be used not only in the respective combination indicated, but also in any other combinations or alone without going beyond the scope of the present invention.
Preferred embodiments of this invention are illustrated in the drawings and explained in greater detail in the following description.